What Is the Metacarpophalangeal Joint?

Metacarpophalangeal joint metacarpophalangeal joint, consisting of the small head of the metacarpal and the base of the proximal phalanx (section 1), the thumb metacarpophalangeal joint belongs to the tackle joint, and the remaining four fingers are ball and socket joints.

Metacarpophalangeal joint metacarpophalangeal joint, consisting of the small head of the metacarpal and the base of the proximal phalanx (section 1), the thumb metacarpophalangeal joint belongs to the tackle joint, and the remaining four fingers are ball and socket joints.

Chinese name

Metacarpophalangeal joint

Foreign name

metacarpophalangeal joint

Constitute

The small head of the metacarpal and the base of the proximal phalanx

Number

5 in total

3D Morphology of Metacarpophalangeal Joints

Observation specimen (Fig. 1): viewed from the sagittal plane, the palmar side of the metacarpal head is wider, and a curve with a gradually increasing radius of curvature is formed from the dorsal side to the palm side. Viewed from the coronal plane, the metacarpal head is pear-shaped, with the palmar sides extending to the sides to form two ridges. The radial ridge is slightly larger than the ulnar ridge, especially in the second and third metacarpal heads. The articular surface of the first metacarpal head is nearly square, with less curvature than the other four metacarpal heads; the second metacarpal head is larger and slightly irregular in shape; the third metacarpal head is round and prominent; 3 is approximate, but smaller. The morphology of the phalangeal base of each proximal segment is similar, all of which are oval-shaped with a central depression and no significant difference in size.

figure 1

Metacarpophalangeal blood supply

The metacarpophalangeal joints each have an average of 7.7 joint branches, which fully demonstrates that the metacarpophalangeal joints have a rich blood supply. The ratio of the articular branch to the palmar side on the dorsal side of the metacarpophalangeal joint capsule is 2: 1. This shows that the dorsal joint branch of the joint capsule is more than the palmar joint branch, and each joint branch originates from an adjacent artery. Observations revealed that the flexure, ulnar dorsal side, and upper and lower joint branches are in a radial pattern from the periphery of the joint capsule to the center in different directions and in different directions, and kiss each other to form a mesh in the fiber layer. This ensures that under the local compression of the metacarpophalangeal joints, the blood supply and the body surface projection of the joint branch on the ulnar dorsal side can be obtained. It is the intersection point of 4/5 and 1/5 over the full length of the dorsal side of the metacarpal. The surface projections of the infra-articular and ulnar dorsal joints are the points of intersection of the proximal phalanx and the middle. The length of the superior and inferior joint branches of the torso, ulnar side, and the outer diameter of the proximal end are consistent with the physiological length and functional status of each finger. For the first, second, and third metacarpophalangeal joints, you can choose the 1st and 2nd dorsal metacarpal artery located on the superficial surface of the dorsal interosseous muscle. Their average outer diameters are respectively. .sm and l.Zmm, and can be 38mm and 43mm away from the proximal end. The radial artery (2.7 mm in outer diameter) can also be found at the styloid process. The fourth and fifth metacarpophalangeal joints can be selected from the 3rd and 4th dorsal metacarpal arteries, which have an average outer diameter of 1.0 mm and o. smm, and can be free 35mm and 32mm to the proximal end. You can also choose the ulnar palmar artery of the little finger with an outer diameter of 1.2mm. The superficial veins and cutaneous nerves of the hand are well documented. The thumb vein is not arched and has an outer diameter of 1.smm. The palmar dorsal veins are 1.3mm, 1.1mm, and 1.omm. The veins of the thumb, index finger, and middle finger are biased to the flexion side, and the veins of the ring finger and little finger are biased to the ulnar side. To vein.

Metacarpophalangeal joints and joints

The bones of the hand mainly include 2 phalanxes of the thumb, 3 phalanxes of the middle, ring, little finger, 5 metacarpals and 8 carpal bones. In addition to the metacarpophalangeal joint, the interphalangeal (distal and near) joints, the joints also include the carpal metacarpal joint and the wrist joint (the radial bone is combined with the boat, the moon, and the triangular bone). These bones and joints constitute a stent of the hand to maintain the normal function of the hand. Once the structure is destroyed by war or trauma, the hand cannot perform the normal function.

Functional position of metacarpophalangeal hand

The functional position of the hand is the position in which the hand can fully perform its functions before exercise. At this time, the forearm is in a semi-rotated forward position, with the wrist extended 25 ° -30 °, the ulnar side deflected by 10 °, and the thumb fully abducted. The interphalangeal joints are slightly flexed, in the opposite palm position, and the other four fingers are separated. The degree of joint flexion varies, that is, metacarpophalangeal joint flexion is 30 ° to 40 °, proximal interphalangeal joint flexion is 60 ° to 80 °, and distal interphalangeal joint flexion is 10 ° to 15 °. The functional position is the preparation posture before performing various activities. It is relatively easy to restore its effective range of motion in this position, because the thumb is in the full palm position, as long as the other four fingers can move the joint to flex slightly to complete a certain Function, so when dealing with hand warfare, trauma, especially fractures, tendon injuries, the hand should be fixed in the functional position. Sometimes in order to ensure that the tendons, nerves, and vascular ruptures are sutured firmly or in a more relaxed position to facilitate healing, a protective braking position, that is, a non-functional position for temporary braking, can be used. For example, after the wrist median nerve, ulnar nerve, or flexor tendon is sutured, it is safer to fix the wrist joint at 40 ° flexion position for 3 weeks; meanwhile, the metacarpophalangeal joint is flexed nearly 80 °, and the interphalangeal joint is in a natural straight position. When repairing the dorsal tissue, the wrist joint is braked in the extended position and the metacarpophalangeal joint is flexed at least 10 °.